When should I take a test?

Cass
'm 5 days late I had a little brown period very light 3days b4 my AF was suppose to come.  Now it's gone. Took a pregnancy test 3 days ago in the afternoon, got a BFN.  I have a lot clear gooie stuff. Could I be pregnant? Was it to soon to take a test? What are my chance of being pregnant? Should I be having any symptoms this early? I just have lower back pain that's it.